Artificial leather



Patented June 21, 1938 UNITED STATES PATENT oFFic ARTIFICIAL LEATHER Merlin Martin Brubaker, Wilmington, Del., and

Leo Phillip Hubbuch, Springfield, Pa., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application June 15, 1936, Serial No. 85,416

2 Claims.

This invention relates to artificial leather products and more particularly to fabrics coated with cellulose derivative compositions.

This application is a continuation in part of 5 our application Serial Number 691,094, filed September .26, 1933.

This invention has as an object the preparation of new and useful coated fabrics. A further object is the manufacture of artificial leather products comprising cellulose nitrate coated fabrics possessing exceptional toughness, abrasion resistance, and durability. A still further object is the production of coated fabrics of this kind in which glyceride of the coconut oil type, i. e., a fatty acid glyceride having an iodine number of less than 35 and a saponification number of 200 to 300. It has been discovered that glycerides of the coconut oil type may be modified so as to render them of great utility in cellulose derivative compositions applied over flexible fabrics.

In order that softening agents for cellulose derivative compositions shall retain their initial properties on aging it has been found that the softening agent should be almost saturated to prevent its oxidation and the detrimental effect of this oxidation on the remainder of the cellulose derivative composition. Hereinafter the term saturated when used with reference to glycerides of the coconut oil type includes only those glycerides with an iodine number below 35. An iodine number of about 85 corresponds roughly to a glyceride from a long chain fatty acid containing one double bond. The saponification 'values of a few pure glycerides may be listed, thus, tristearin 189, tripalmitin 208, trilaurin 263, tricaprin 304. The saponification value is the number of milligrams of potassium hydroxide required to saponify one gram of the oil, fat or wax.

Theexamples given below in which the parts are by weight illustrate the more specific details of the invention. The first three of these examples describe the preparation of the softener constituent of the cellulose derivative coat.

00 Phthalic anhydride (mol. wt. 148) 22.4

The diethylene glycol, coconut oil. and glycerol are heated together in a closed kettle, fitted with a reflux condenser and stirrer for one hour at 250 C., or until a test spot of the mixture on cooling does not become cloudy. This alcoholysis step is facilitated by very rapid stirring. At the completion of the alcoholysis the charge is cooled slightly and the phthalic anhydride is added. Steam is blown through the condenser, and CO2 is blown through the charge which is stirred rapidly and heated for six hours at 225 C. At this point, the acid number of the product is approximately 5.0. The charge is then cooled. The re sulting product is a. light brown oil of viscosity around nine poises. In place of the oil, it is understood that the requisite amounts of oil acids and glycerol may be used and the initial alcoholysis step avoided. However, the alcoholysis method is preferred inasmuch as it gives a better product.

In place of diethylene glycol, some other dihydric alcohol such as ethylene glycol may be used. .The following example illustrates this use:

7 Example II Constituent: Parts Ethylene glycol (mol. wt. 62) 10.30 Coconut 011 (mol. wt. 662) 67.30 Glycerol (mol. wt. 92) 0.10 Phthalic anhydride (mol. wt. 148) 22.30

The ethylene glycol, coconut oil, and glycerol are heated together in a closed kettle fitted with a reflux condenser and stirred for 1 /2 hours at 200 C. until some alcoholysis has occurred. This alcoholysis step is facilitated by very rapid stirring. The charge is then cooled and the phthalic anhydride added. Steam is blown through the condenser and CO2 is blown through the charge which is stirred rapidly and heated for four hours at 225 C. At this point, the acid number of the product is approximately 5.0. The charge is then cooled. The resulting product is a light brown oil of a viscosity around nine poises.

Other proportions of the polybasic acid--dihydric alcohol constituent and the saturated glyceride of the coconut oil type may be used as the following example will illustrate:

Example III Constituent: Parts Diethylene glycol (mol. wt. 106) 19.18 Coconut oil (mol. wt. 662)..- 43.70 Coconut oil acids (mol. wt. 208 22.70 Phthalic anhydride (mol. wt. 148) 14.42

hours heating, the charge shows an acid number of around 2.0. The product, when cooled, is a light red oil of a viscosity around five poises. In the above example both the coconut oil and the coconut oil acids are used. This is found essential in order to obtain the desired composition.

The following two examples illustrate compositions which contain the foregoing softeners and which are applied to the flexible fabric in the manufacture of my improved artificial leather products:

ExampleIV Parts Softener of Example I'1I 18.4 Extracted pyro nitrocellulose 11.8 Lithopone pigment 13.6 Ethyl acetate 22.4 Ethyl alcohol. 33.8

This composition, when spread o'n clothand suitably dried, gives an artificial leather which is superior to that with castor oil or coconut oil as the softener.

Example V Parts Softener of Example I 20.8 Extracted pyro nitrocellulose 11.3 Lithopone pigment 14.4 Ethyl acetate 21.4 Ethyl alcohol -4 32.1

The softeners should not for the best results contain substantially more than the amount of coconut oil glyceride used in the above examples. As the proportion of the oil glyceride gets greater than about 70% the advantageous properties, particularly with respect to toughening action and freedom from exudation, become less pronounced. The minimum amount of the coconut oil glyceride is about 40% and the optimum results are obtained from to s In the foregoing description the invention has been outlined in relation to coconut oil, ethylene glycol, diethylene glycol, and phthalic anhydrlde. Other glycerides of the coconut 011 type, other dihydric alcohols and other dibasic acids may, however, be used in varying proportions. Changes in the ratio of glyceride to dihydric alcohol-dibasic acid complex are of course necessary depending on the glyceride, the dihydric alcohol, and the dibasic acid. For coconut oil other saturated glycerides of the coconut oil type such as those mentioned above may be susbstituted. In place of diethylene glycol or ethylene glycol, other dihydric alcohols such as triethylene glycol, butylene glycol, dipropylene glycol, octadecanediol, monobenzylin, propylene glycol, monoethylin, monomethylin, may be used. Other dibasic acids or their equivalent derivatives such as the anhydride may be used, such as succinic, adipic, diphenic, camphoric, tartaric, malic, pimelic, sebacic sube ic, azelaic, etc., acids.

The methods of preparing the softeners used in our new products may vary considerably. The

'- preferred method is to heat the saturated glyceride with the dihydric alcohol so as to obtain alcoholysis, and to prevent as much as possible the formationof the dibasic acid-dihydric alcohol complex when the dibasic acid is later added. It is, however, possible to prepare similar products by heating all of the constituents together simultaneously or, in certain cases, by forming the dihydric alcohol-dibasic acid complex first and heating this with the saturated glyceride. 'I'krlg acids of-the saturated glyceride may 106* heated with the requisite amount of glycerol in the presence of one or more of the other constituents, the remaining ingredients being added at a later stage of the heating to produce suitable softeners. The .resin may also be prepared in the presence of an inert solvent as described in the co-pending application of M. M. Brubaker, Serial Number 421,585, filed January 1'7, 1930. Experience, however, has shown that the alcoholysis method for the preparation of non-blooming, stable softeners is by far the best.

The total effect of a softener for artificial leather compositions is a resultant of two distinct effects, 1. e., viscosity and solvent action. Increasing the viscosity of the softener, within certain limits, increases the strength and bind ing power of the coating composition, increases its exudation temperature and decreases its pliability. Increasing the solvent action of the softener, within certain limits, decreases the strength of the coating composition, increases its exudation temperature and increases its pliability. By

proper adiustment of these two effects it is pos nut oil is heated with a dihydric alcohol such as diethylene glycol and ester interchange occurs with the partial formation of a dihydric alcohol ester which has some solvent action.

By adding phthalic anhydride and esterifying, the viscosity of the softening agent is increased due to the formation of some dibasic acid-dihydric alcohol complex. If the viscosity of the softener is increased too much (roughly, greater than 250 poises) by the formation of a large proportion of the dibasic acid-polyhydric alcohol complex, e. g. that obtained from more than 40% phthalic anhydride, it is not possible to obtain a tough, abrasion resistant film of the proper pliability with a cellulose derivative even by increasing the ratio of softening agent to the cellulose derivative. In other words without the combined dibasic acid-dihydric alcohol reaction products, theglycerides fail to give binding power to the other ingredients of the artificial leather coating composition, or else bloom from the film; with too great a proportion of the combined dibasic acid-dihydric alcohol reaction products, the resulting softeners cause brittleness of the coating composition.

'Giycerides whose saponification values are higher than 300, even after modification by the herein described process show too much solvent action on the cellulose derivative composition thereby reducing its toughness. Glycerides whose saponification values are lower than 200 are, even after modification, too waxy and bloom from the film. A number of saturated glycerides of the coconut oil type are available for use. The large majority, however, are either not compatible with the cellulose derivative or else, due to their solid nature at room temperature tend to bloom from,

a film containing them, i. e. tend to form a white,- greasy, film on the surface of the cellulose derivative compositions. By modifying these saturatedglycerides in the manner of this invention oils ranging in viscosity from about 1 poise to' In making these new castor oil substitutes the non-solvent glyceride such as coco-- about 250 poises are obtained. These are readily compatible with cellulose nitrate and ethyl cellulose and show no tendency to bloom. Their compatibility with cellulose acetate is not particularly advantageous. While the advantage of non-blooming is pronounced, it is not the paramount one of the invention. In the judgment of the initial quality of artificial leather, two factors are important. The first is that the softening component of the cellulose derivative and particularly cellulose nitrate coating composition must not exude or come out on the surface of the film in the form of oil drops at too low a temperature. In general, exudation much below 60 C. indicates an incompatible film. A softener in a cellulose nitrate composition which does not exude until the temperature is at least 60? is a fair softener. One which exudes only above 80 is a good softener, and an excellent softener exudes only at above 100. The optimum is, of course, no exudation at any reasonable temperature. The second factor of importance, in the judgment of the initial quality of artificial leather, is the ability of the coated fabric to withstand scrubbing. By the term scrubbing is meant rubbing two coated faces of the artificial leather together in a suitable manner until the coating is broken. The number of scrubs is considered a measure of the toughness of the coating.

The superiority of products described herein is illustrated by the following table which gives lar weight than stearic acid are excluded from the scope of the present invention because of this objectionable feature. Glycerides lower than tricaprin are also excluded since products of bad odor, high volatility and extreme solvent action are formed from such glycerides.

The superiority of our improved coated fabrics over similar products now in use for artificial leather isv best shown by the following compari- SOD:

Y Exudasoftener Initial on Percent Composition number deteriora- N/C mm of scrubs tion Example IV :45 120 06 +50 Same as Example IV with castor oil in place of the new softener :30 145 63 +90 Same as Example IV with coconut oil in place of the new softener 70:30 100 77 +71 The percent deterioration represents the decrease in scrub alter four weeks aging at 65 C.

Ratio of softener to nitrocellulose required to give a coating of medium pliability when 30% of pigment is used.

From this it is seen that after four weeks aging at 65 C. the composition of Example IV would still scrub approximately 60 times before breaking, whereas the castor oil composition would scrub only approximately 15 times, and

the coconut oil composition only approximately.

actual results on artificial leathers containing 29 times. In addition, both the castor'oil and different softeners: the coconut oil compositions exuded at tempera- 'Soitener Initial Exudation Softener ingredients Percent W Scrub temuoa Bloom 100.00 7030 100 71 Definite.

sax 19:18 65:45 120 96 None. 14.42 01.30 :38 00:40 180 09 None. 22.40 43.30 8:; 75:25 170 None.

31.00 2-22 13:40 86:15 0 170 None. 44.00 31.90 18 :15 0 None. 41.00 100.00 103.0 0 Low Bad. Castor oil 100.00 70:30 65 None.

' Improved castor oil substitutes oi the present invention. Balsams, i. e., resinous products.

Ratio of softener to nitrocellulose required to give a coating of medium pliability when 30 percent of pigment is used.

Typical balsams of the modified polyhydric alcohol-polybasic acid resin type outside of the range of the products of this invention are unsuitable as castor oil substitutes in artificial leather compositions because of the brittleness they ification.

It will be seen from the foregoing description that'we have developed an improved cellulose derivative coating perculiarly adapted to the manufacture of artificial leather products by reason of its extreme toughness, at practical pliabilities for artificial leather products, coupled with good 2,121,es;s- V

- thetic oil which comprises in chemical combination phthalic acid, a dihydric alcohol, and 40 to 70% by weight of the glycerlde of coconut oil, said' coating having an exudation temperature greater than 80 C. and having a high resistance 5- to breaking upon rubbing coated faces of the arti ficial leather product together.

2. The artificial leather product set forth in claim 1 in which the coconut oil glyceride is present in amount from about 60 to 65% byweight. 10

mm MARTIN BRUBAKER. LEO PHILLIP maven. 

